Lexus ES: Master Reservoir Level Malfunction (C1202)

DESCRIPTION

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	MIL	Note
C1202	Master Reservoir Level Malfunction	1126	Either of the following is detected: The brake fluid level warning switch signal circuit is open for a certain period of time. The reservoir level is low for a certain period of time.	Open or short in brake fluid level warning switch (brake booster with master cylinder assembly) Brake fluid leaks Open or short in wire harness Low brake fluid Skid control ECU (brake booster with master cylinder assembly)	Comes on	INF Code 1126: SAE Code C1202 Electronically controlled brake system DTC HINT: DTC C1202 (INF code 1126) is cleared when the conditions return to normal.

MONITOR DESCRIPTION

When the power switch is on (IG) and the fluid level warning switch (brake booster with master cylinder assembly) is on for a certain amount of time, the skid control ECU (brake booster with master cylinder assembly) judges that the brake fluid level in the reservoir is low and illuminates the MIL and stores this DTC.

MONITOR STRATEGY

Related DTCs	C1202: Brake master cylinder reservoir assembly level too low
Required Sensors/Components(Main)	Brake fluid level warning switch (brake booster with master cylinder assembly) Skid control ECU (brake booster with master cylinder assembly)
Required Sensors/Components(Related)	-
Frequency of Operation	Continuous
Duration	20 seconds
MIL Operation	Immediately
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored	None
Power switch	On (IG)

TYPICAL MALFUNCTION THRESHOLDS

One of the following conditions is met	-
Brake fluid level warning switch state	On
Brake fluid level warning switch state	Open circuit
Serial communication with IC	Invalid

COMPONENT OPERATING RANGE

All of the following conditions are met	-
Power switch	On (IG)
Brake fluid level warning switch state	Off
Serial communication with IC	Valid

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".

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PROCEDURE

1.

CHECK DTC

(a) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(b) Turn the power switch off.

(c) Turn the power switch on (IG).

(d) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1202 is output.	A
DTC C120F is output with DTC C1202.	B

B

GO TO DTC (C120F)

A

2.	CHECK BRAKE FLUID LEVEL

(a) Check that the brake fluid level is sufficient.

HINT:

If the fluid level is low, check for fluid leaks, and repair as necessary.

(1) Check for brake fluid leaks (connection between the brake booster pump assembly, brake master cylinder reservoir assembly (brake booster with master cylinder assembly), brake booster with master cylinder assembly, and wheel cylinders).

HINT:

If no leaks exist, add and adjust fluid using the Techstream.

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(2) Check the thickness of the brake pad lining.

for Front Brake: Click here

for Rear Brake: Click here

HINT:

If the thickness is less than the standard, replace the brake pads with new ones.

(b) Check that there are no leaks from the connections between the brake booster pump assembly and brake booster with master cylinder assembly.

HINT:

As a visual check is very difficult, perform the check with the following procedure.

(1) Bleed the air from the brake system.

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(2) Turn the power switch off.

(3) Disconnect the A44 brake pedal stroke sensor assembly connector.

(4) Select the Data List on the Techstream.

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Chassis > ABS/VSC/TRAC > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
MT Voltage Value	MT voltage value	Min.: 0.00 V, Max.: 20.00 V	Pump motor off: 0.00 V Pump motor on: 12.00 V	-
Accumulator Pressure	Accumulator pressure output value	Min.: 0.00 MPa, Max.: 24.48 MPa	15.00 to 21.00 MPa (Pressure stable and pump motor stopped)	When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator

Chassis > ABS/VSC/TRAC > Data List

Tester Display
MT Voltage Value
Accumulator Pressure

(5) Depress the brake pedal several times to operate the pump motor, then wait until it stops.

(6) After the pump motor stops, wait for 30 seconds, then check the drop in the accumulator pressure sensor output value and the state of the pump motor.

Result	Proceed to
The drop in the accumulator pressure sensor output value is less than 2.50 MPa 30 seconds after the pump motor stops, and the pump motor does not operate within 30 seconds after the pump motor stops.	A
The drop in the accumulator pressure sensor output value is 2.50 MPa or more 30 seconds after the pump motor stops, or the pump motor operates within 30 seconds after the pump motor stops.	B

B

CHECK AND REPAIR BRAKE FLUID LEAKS OR ADD FLUID

A

3.	INSPECT BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY (BRAKE FLUID LEVEL WARNING SWITCH)

(a) Turn the power switch off.

*a Component without harness connected (Brake Fluid Level Warning Switch (Brake Booster with Master Cylinder Assembly))

(b) Reconnect the A44 brake pedal stroke sensor assembly connector.

(c) Remove the brake master cylinder reservoir filler cap assembly.

(d) Make sure that there is no looseness at the locking part and the connecting part of the connector.

OK:

The connector is securely connected.

(e) Disconnect the A4 brake fluid level warning switch (brake booster with master cylinder assembly) connector.

(f) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

(g) Measure the resistance according to the value(s) in the table below.

HINT:

A float is located inside the brake master cylinder reservoir assembly (brake booster with master cylinder assembly). Its position changes according to the level of brake fluid.

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (LBL) - 1 (GND)	Brake fluid level warning switch (brake booster with master cylinder assembly) off (float up)	1.84 to 2.16 kΩ
2 (LBL) - 1 (GND)	Brake fluid level warning switch (brake booster with master cylinder assembly) on (float down)	Below 1 Ω (Brake fluid level is low)

(h) If there are no problems after completing the preceding inspection, adjust the brake fluid to the MAX level with the power switch on (IG).

NG

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

OK

4.	CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE FLUID LEVEL WARNING SWITCH (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY))

(a) Make sure that there is no looseness at the locking part and the connecting part of the connector.

OK:

The connector is securely connected.

(b) Disconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.

(c) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

(d) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A45-16 (LBL) - A4-2 (LBL)	Always	Below 1 Ω
A45-16 (LBL) or A4-2 (LBL) - Body ground	Always	10 kΩ or higher
A4-1 (GND) - Body ground	Always	Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.	INSPECT BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY (SWITCH INPUT)

(a) Reconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.

*a Front view of wire harness connector (to Brake Fluid Level Warning Switch (Brake Booster with Master Cylinder Assembly))

(b) Turn the power switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
A4-2 (LBL) - Body ground	Power switch on (IG)	11 to 14 V

NG

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

OK

6.	RECONFIRM DTC

(a) Turn the power switch off.

(b) Reconnect the A4 brake fluid level warning switch (brake booster with master cylinder assembly) connector.

(c) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(d) Turn the power switch off.

(e) Turn the power switch on (READY).

(f) Perform a road test.

(g) Check if the same DTC is output.

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Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1202 is not output.	A
DTC C1202 is output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

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